Still drowsy, Druse mistakes the horseman for a grand statue.
Carter Druse was a Union soldier who was from the Confederate state of Virginia. He had felt a strong devotion to his nation and so joined the Union. One day, after a long 36 hour march, he was placed as a sentry but the exhaustion caused him to sleep.
When he woke up he saw a man on a horse who was looking at their position. At first and for a brief moment in his drowsy state, he thought that it was a grand statue that had been made to commemorate the civil war. This feeling was dispelled by the slight movement of the horse.
d) the narrator even suggested that the white whale, moby d, was ubiquitous and present in every ocean at every moment.